Very recently, topological phonons in solid-state materials have been studied theoretically and experimentally. A series of three-dimensional (3D) materials with rich topological phononic states have been proposed: (i) different types of nodal point phonons [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, including the single and high degenerate Weyl point phonons, ideal type II Weyl point phonons, unconventional triangular Weyl point phonons, Dirac point phonons, triply nodal point phonons, and six-fold nodal point phonons; (ii) different types of nodal line phonons  [13]}, [14]}, [15]}, [16]}, [17]}, [18]}, [19]}, [20]}, [21]}, including nodal-ring phonons, Weyl nodal straight line phonons, helical nodal line phonons, Weyl open nodal line phonons, and hourglass nodal-net phonons; and (iii) multiple nodal surface phonons  [22]}. Among them, double Weyl point phonons in parity-breaking FeSi  [1]} and phononic helical nodal lines in MoB\(_2\)   [15]} have been verified via inelastic X-ray scattering.
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